feat(lanes): add per-feature state + archive core (lane_features) (B)

server/db.js

@@ -432,6 +432,31 @@ db.exec(`
     updated_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now'))
   );
 
+  CREATE TABLE IF NOT EXISTS lane_features (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    lane_id INTEGER NOT NULL,
+    slug TEXT NOT NULL,
+    title TEXT NOT NULL DEFAULT '',
+    branch TEXT,
+    pipeline TEXT NOT NULL DEFAULT 'default',
+    stage TEXT NOT NULL DEFAULT 'idle',
+    stage_since TEXT,
+    status TEXT NOT NULL DEFAULT 'idle',
+    gate_decision TEXT,
+    ci_status TEXT,
+    qc_dev TEXT,
+    stages TEXT NOT NULL DEFAULT '{}',
+    links TEXT NOT NULL DEFAULT '{}',
+    notes TEXT,
+    archived_at TEXT,
+    created_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now')),
+    updated_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now')),
+    UNIQUE (lane_id, slug),
+    FOREIGN KEY (lane_id) REFERENCES lanes(id) ON DELETE CASCADE
+  );
+
+  CREATE INDEX IF NOT EXISTS idx_lane_features_lane ON lane_features(lane_id);
+
   CREATE INDEX IF NOT EXISTS idx_lanes_session ON lanes(session_id);
 `);
 
@@ -519,6 +544,22 @@ db.prepare(
   "CREATE UNIQUE INDEX IF NOT EXISTS idx_lanes_slot ON lanes(slot) WHERE slot IS NOT NULL"
 ).run();
 
+// Migrate: per-feature state (B). `active_feature_id` points at the
+// lane_features row currently "live" (unarchived) for this lane — null for a
+// lane that has never called `ccam feature activate`, which is why this
+// column is nullable and every downstream reader of a lane row is unaffected
+// by its addition. ON DELETE SET NULL, not CASCADE: deleting the ACTIVE
+// feature row (which normally only happens via cascade when the LANE itself
+// is deleted, at which point this column is moot anyway) must never leave a
+// dangling id on a lane row that still exists.
+try {
+  db.prepare("SELECT active_feature_id FROM lanes LIMIT 1").get();
+} catch {
+  db.prepare(
+    "ALTER TABLE lanes ADD COLUMN active_feature_id INTEGER REFERENCES lane_features(id) ON DELETE SET NULL"
+  ).run();
+}
+
 // Migrate: link agent rows to a workflow run. Workflow inner-agents are already
 // ingested as subagents (same subagents/ dir); these columns add the grouping +
 // phase that the run journal provides. Additive, safe on existing DBs.